This invention relates to electricity meters, eg watthour meters, and is more particularly concerned with electricity meters incorporating means for counteracting certain methods of fraud.
One common method of defrauding an electromechanical electricity meter of the rotating disc type is to slow down the rotating disc by external means, such as a piece of wire arranged to bear on the disc or a powerful magnet. However, with the advent of electronic meters, for example of the kind described and claimed in U.S. Pat. No. 4,359,684, this method of fraud will no longer be possible.
Another common method of defrauding an electricity meter is to connect an external shunt in parallel with the meter. More specifically, the external shunt is connected in parallel with the live wire of the power distribution circuit in which the meter is connected, i.e. the wire in which the current sensor of the meter is connected, so that at least some of the current used by the consumer bypasses the meter and therefore does not contribute to the energy measurement effected by the meter. This method of fraud can be used with both electromechanical and electronic meters, and it is an object of the present invention to counteract it.